Carrier 58PHA/PHX Speed Selection, Furnace Overheating Hazard, Check Safety Controls

Table 11 – Speed Selection

COLOR	SPEED	AS SHIPPED
Gray	5	COOL
Yellow	4	SPARE
Blue	3	HEAT
Orange	2	SPARE
Red	1*	CONT FAN

* Continuous---blower speed---as shipped default

!CAUTION

FURNACE OVERHEATING HAZARD

Failure to follow this caution may result in reduced furnace life.

Recheck temperature rise. It must be within limits specified on the rating plate. Recommended operation is at the mid-point of rise range or slightly above.

6.Set thermostat heat anticipator.

a.Mechanical thermostat - Set thermostat heat anticipator to match the amp. draw of the electrical components in the R-W circuit. Accurate amp. draw readings can be obtained at the wires normally connected to thermostat subbase terminals, R and W. The thermostat anticipator should NOT be in the circuit while measuring current. (1.) Remove thermostat from subbase or from wall.

(2.) Connect an amp. meter as shown in Fig. 54 across the R and W subbase terminals or R and W wires at wall.

(3.) Record amp. draw across terminals when furnace is in heating and after blower starts.

(4.) Set heat anticipator on thermostat per thermostat instructions and install on subbase or wall.

b. Electronic thermostat: Set cycle rate for 4 cycles per hr.

7.Adjust blower off delay The blower off delay has 4 adjustable settings from 90 sec to 180 sec. The blower off delay jumpers are located on the furnace control board. (See Fig. 24.)

To change the blower off delay setting, move the jumper from one set of pins on the control to the pins used for the selected blower off delay. Factory off delay setting is 120 sec.

8.Set airflow CFM for cooling

Select the desired blower motor speed lead for cooling airflow. See Table 5-Air Delivery-CFM (With Filter). See Table 11 for lead color identification.

Check Safety Controls

The flame sensor, gas valve, and pressure switch were all checked in the Start-up procedure section as part of normal operation.

1.Check Main Limit Switch(es)

This control shuts off combustion control system and energizes air-circulating blower motor, if furnace overheats. By using this method to check limit control, it can be established that limit is functioning properly and will operate if there is a restricted duct system or motor failure. If limit control does not function during this test, cause must be determined and corrected.

a.Run furnace for at least 5 minutes.

b.Gradually block off return air with a piece of cardboard or sheet metal until the limit trips.

c.Unblock return air to permit normal circulation.

d.Burners will re-light when furnace cools down.

2.Check draft safeguard switch.

The purpose of this control is to cause the safe shutdown of the furnace during certain blocked vent conditions.

THERMOSTAT SUBBASE TERMINALS WITH THERMOSTAT REMOVED (ANITICIPATOR, CLOCK, ETC.,

MUST BE OUT OF CIRCUIT.)

HOOK-AROUND AMMETER

R Y W G

10 TURNS

FROM UNIT 24-V

CONTROL TERMINALS

EXAMPLE:	5.0 AMPS ON AMMETER	=	0.5 AMPS FOR THERMOSTAT
	10 TURNS AROUND JAWS		ANTICIPATOR SETTING

A96316

Fig. 54 - Amp. Draw Check with Ammeter

a.Verify vent pipe is cool to the touch.

b.Disconnect power to furnace and remove vent connector from furnace vent elbow.

c.Restore power to furnace and set room thermostat above room temperature.

d.After normal start-up, allow furnace to operate for 2 minutes, then block vent elbow in furnace 80 percent of vent area with a piece of flat sheet metal.

e.Furnace should cycle off within 2 minutes. If gas does not shut off within 2 minutes, determine reason draft safeguard switch did not function properly and correct condition.

f.Remove blockage from furnace vent elbow.

g.Switch will auto-reset when it cools.

h.Re-install vent connector.

NOTE: Should switch remain open longer than 3 minutes, furnace control board will lockout the furnace for 3 hours. To reset furnace control board, turn thermostat below room temperature or from HEAT to OFF and turn 115v power OFF, then back ON.

3.Check Pressure Switch

This control proves operation of the draft inducer blower.

a.Turn off 115-v power to furnace.

b.Disconnect inducer motor lead wires from wire harness.

c.Turn on 115-v power to furnace.

d.Set thermostat to “call for heat” and wait 1 minute. When pressure switch is functioning properly, hot surface igniter should NOT glow and control diagnostic light flashes a status code 32. If hot surface igniter glows when inducer motor is disconnected, shut down furnace immediately.

e.Determine reason pressure switch did not function properly and correct condition.

f.Turn off 115-v power to furnace.

g.Reconnect inducer motor wires, replace outer door, and turn on 115-v power.

h.Blower will run for 90 sec before beginning the call forheat again.

i.Furnace should ignite normally.

58PHA

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